ISEP 2006

ENVIRONMENT AND AIR TRAFFIC NOISE

IGOR ŠTIMAC, B.Eng. E-mail:[email protected] Zračna luka Pleso bb, 10000 Zagreb, Hrvatska JURICA IVANIŠEVIĆ, B.Eng. E-mail:[email protected] Zračna luka Zagreb Pleso bb, 10000 Zagreb, Hrvatska mr.sc ZLATKO SVIBEN,. E-mail: [email protected] Poštanska i telekomunikacijska škola Trg J. F. Kennedya 9, 10000 Zagreb, Hrvatska

pollution of soil and water at airports. At its 50th Assembly, ABSTRACT IATA brought a Resolution on environment which fully supported the ICAO initiative about the revision of the The increase in the number of flights makes air traffic a restrictions in issuing the certificates which confirm that the serious problem of the present. Modern, jet aircraft generate deafening noise in the approach and takeoff of aircraft. Noise is airlines satisfy the criteria of noise, harmful exhaust emissions generated by aircraft engines letting out at high speed vortex and chemicals, all with the aim of reducing the negative impact exhaust gases, and in case of supersonic aircraft there is additional of air traffic on the environment. Adverse impact of thunder due to impact waves that follow takeoff or landing of anthropogenic polluters, including aircraft, affects to a great aircraft. In order to solve the problem of aircraft noise, some extent the global ecological balance in three main indications: alternative solutions will have to be implemented, such as - change in the balance of earth radiation due to replacement of the current air fleet by a new generation of aircraft anthropogenic greenhouse effect, related to the change or some immediate solutions such as the installation of hush-kits of global climate; and some special parts in the aircraft, which also affects the - change in the ozone in the atmosphere that affects the reduction of aircraft noise. Fast development of airports, resulting in problems related to noise, require finding of ways in which to intensity of radiation on the earth surface; harmonize development, modernisation of air traffic and the - change in the oxidation capacity of atmosphere due to “potential noisy adversaries” that occur as a consequence of the increase in the tropospheric concentration of ozone. technological development of airports. It is interesting to know the Regarding protection, today’s technology can respond to many values that define the noise as well as the values within which they requirements which first of all means the improvement of range, according to the valid regulations. In this way other traffic aircraft structure assemblies. The first aspect is the noise participants can understand the environment and take the attitude generated by aircraft, and the second aspect represents harmful of an active participant – define themselves to the measure of the emissions. The level of noise and the harmful exhaust emissions human. are regulated by the international (ICAO) and national regulations. The problems related to aircraft noise appeared Key words: noise, ecology, aircraft, airport when the number of operations during one day at one airport increased to such an extent that lives of the population living in 1. INTRODUCTION - CURRENT CONDITION the vicinity became intolerable. The introduction of jet aircraft resulted in protests of the population living around the airports Traffic degrades and devastates the environment and due to noise. It was impossible to live, especially below the every project of traffic development either on land, in the air, or approach and takeoff paths. Noise is generated by aircraft on water, needs to evaluate the volume of negative impact on engines which produce fast vortex exhaust gases. In case of the environment. The first knowledge about the harmful impact supersonic aircraft there is also additional thunder due to impact of traffic on the environment dates back to the sixties of the 20th waves which follow the takeoff or landing. When speaking of century. Today, life would be unthinkable without the transport noise generated by aircraft we think of the subjective feeling means, and yet their increase undoubtedly leads to the that an observer on ground feels due to the aircraft-generated destruction of the natural flora and fauna. An important noise. For noise measuring, a large number of measuring units milestone in the development of air traffic is the introduction of was defined and the most common is the decibel (dB). the jet propulsion in the sixties. The main ecological criteria Under the pressure of the public and the authorities, the airports related to international commercial aviation include aircraft have introduced additional measures to reduce the negative noise, aircraft engine emission, handling of waste material and impact of noise on the environment: by restricting the

ISEP 2006 operations of noisy aircraft, by introducing certain procedures 1. the sum of EPNdBs for which the stipulated limits in approach and takeoff in order to reduce noise, by introducing were exceeded, does not exceed the value of 4 EPNdB approach-takeoff paths above less populated or unpopulated (for Chapter 2) i.e. 3 EPNdB (for Chapter 3 aircraft), areas, by banning night air traffic at airports, by sound- 2. value of EPNdB, for which the noise is greater at any insulation of houses i.e. buildings, by zoning of space, by point, does not exceed 3 EPNdBs (for Chapter 2) i.e. 2 moving. EPNdBs (for Chapter 3 aircraft), 3. the higher realized noise at one or two points is compensated by such reduction of noise in another or other points.

2. SOURCE OF AIRCRAFT NOISE

The basic source of aircraft noise is the power plant. Propeller aircraft generate significantly lower noise compared to others. Noise generated by an operating turbo jet power plant occurs in all the basic engine elements. Noise generated by fans and compression spreads partially forwards and exits through Figure 1: Contours of noise of 100 EPNdB in approach and the suction nozzle, and partly spreads backwards and leaves the takeoff for a flight range of up to 1500 km engine through the fan nozzle. Noise generated in the

combustion chamber exits through the central engine nozzle. In order to standardize the measurement of noise intensity in Also the mixing of the ambient air with the jet of exhaust gases certifying aircraft, ICAO stipulated standard conditions and produces certain noise since they flow at very high speed. Fan reference points in the vicinity of runways, determining the in flight generates also additional source of noise, and this is level of noise in landing or takeoff. These points are: noise that due to the interaction of fan blades and stator as well 1. Takeoff point (point A) – point on the runway axis and as the influence of their mutual location, wide range noise, that 6500 meters from the runway threshold. At this point is generated under the influence of the conversion of work from the noise intensity in the takeoff phase is measured, the fan blades on the air flow with the aim of obtaining maximal 2. Approach (point B) – point located on runway axis and effect of compression on a minimal space and whirring noise 2000 meters from the runway threshold. At this point which results from supersonic speed of airflow at the fan blade the noise intensity in landing phase is measured. tips. 3. Lateral point (point C) – point at lateral distance of The noise reduction can be influenced by using the material 650 meters from the runway. In this point the intensity which absorbs sound into the engine flow channel, by mixing of noise in the takeoff phase is also measured. outside cold and interior warm flow of air or by installing hush- kits at the exit of the central nozzle. The first reduction of noise occurred with the appearance of omni-flow turbo-jet power plants with low level of two-flow, and later with the occurrence of power plants with high level of two-flow. Another element which causes noise is the planner. Noise generated by planner results from pulsing of aerodynamic forces on the wing, by the existence of turbulent boundary layer and vortex which occurs in air flowing around the surfaces of Figure 2: Noise measurement points wings, fuselage and tail planes, as well as the airflow around landing gears, flaps and various other protrusions on the Every point at which the level of noise is measured has its fuselage. During takeoff the level of noise caused by the limit values compared to the aircraft weight. These values have planner is irrelevant, whereas noise generated in approach or to be complied with. Every country determines for itself its limit landing is of great importance and regarding intensity can be value. The new noise measurement unit is called EPN dB compared to the noise of power plants. According to ICAO (Effective Perceived Noise decibel). Since there are no precise standards ANNEX 16 Chapter 2, the noise level of planner is mathematical methods to determine the noise level for the stipulated at 8-10 EPNdB lower than the level of total noise, mentioned three points, during the design of aircraft the final and in Chapter 3 the level has been stipulated at 5-7 EPNdB of values of noise level are determined experimentally by the total noise intensity. recording the aircraft. During recording it may happen that the aircraft exceeds the limit noise level stipulated by the regulation at one or two points. Such aircraft may get the certificate for the satisfaction of noise level if:

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3. METHODS OF AIRCRAFT NOISE REDUCTION approach. The standard procedure represents aircraft landing from the altitude of 1500 – 2000 ft above the airport of landing. There are two approaches in the global solving of the In this flight the pilot receives first the signal of the marker ecological problem of noise. The first one is technical, and it is bringing the aircraft to the runway axis i.e. line that matches the related to hush-kitting the engine in exploitation. Hush kit is runway axis. Flying in that plane the pilot accepts the dive angle used as an addition to the final part of the jet engine and it signal (which is at the angle of 3 degrees in relation to the allows conversion of aircraft into FAA Chapter 3 standard on horizontal plane point A), and then starts to dive. Flying at the noise reduction. These parts have to be resistant to very high dive angle the pilot brings the aircraft to the runway threshold temperatures, high vibrations and high pressure, as well as to the altitude of 15 metres, and then starts landing. During the engine thrust. whole flight from the moment the pilot receives the marker Engines are hushed by replacing the engine and by replacing signal, the aircraft is in the landing procedure (extended landing the noisy aircraft by new models. The other approach is the gear, 2 flaps extended, 3 flaps fully extended). For the normal organisational-technological approach which includes flight performance (first in level flight, then in diving) the regulation of the local traffic frequency and staying of aircraft engine thrust must be increased in order to be equal to the total in the air, as well as the rationalisation of the initial-final aircraft drag, and increased thrust generates a secondary operations at airports. The most influential method of noise phenomenon – greater noise generated by the engine itself. reduction is to reduce the source of noise, which means that "quieter" engines and aircraft have to be constructed. Introduction of the quiet fleet of Chapter 3 aircraft will greatly solve the problem of noise, thus allowing exploitation of airport at night, i.e. cancelling the night curfew. Regarding the hush kits, sets for aircraft modification are produces for the most numerous fleet of the Boeing 737-100 and 200 series aircraft, and the modification costs for one aircraft are 2.4 to 3.6 million Figure 3: Standard landing procedure US dollars. From the European carriers, only SAS included the modification sets for DC-9 aircraft along with ordering new Operative procedures used in order to reduce noise in landing Boeing 737-600 aircraft replacing MD-80 and F-28, and are the following: Lufthansa which already obtained the sets for the modification of the Boeing 737-200 fleet. These aircraft will be substituted in the further future by Airbus A-319. Aircraft manufactured in the Increasing the altitude at which the dive angle signal is East have the biggest problem with noise generation exceeding received the permitted noise level. Therefore, their market price has This is a procedure which is defined first since it is most fallen drastically. Such aircraft are used only in domestic traffic, widely used and does not require installation of any special whereas aircraft of western production are used for international equipment on any aircraft nor on the ground. Instead of flying traffic. the aircraft at level flight at the altitude of 450 to 600 metres (1500-2000 ft), in order to receive the dive angle signal, the

pilot performs the level flight at the altitude of 900 metres until 4. OPERATIVE PROCEDURES ALLOWING NOISE receiving the dive angle signal and then the aircraft dives LEVEL REDUCTION towards the runway. Since the flight proceeds until reaching

point A at a higher altitude than the flight in standard Procedure in takeoff – FAA procedure procedure, the noise level on the ground below the flight path In aircraft takeoff there is a procedure formulated by FAA and will be lower. It should be emphasised that in both cases the accepted by ICAO and one version of the procedure formulated flight is performed in the same configuration. According to this by ICAO. According to the first procedure three segments are procedure the noise is reduced until arrival to point A after defined in takeoff, and within each the flight parameters are which the flight proceeds identical to the definitions of the defined that reduce the noise level. The first segment applies standard procedure so that the noise in further flight is the same the technique of aircraft climb which flies up to 1500 ft with the as in the standard procedure. takeoff thrust thus achieving faster moving away from the ground and consequently shorter duration of noise on the ground. This procedure does not require installation of any new equipment, neither onboard aircraft nor on the ground.

Standard landing procedure In landing i.e. approach, there is a larger number of procedures so that these can be compared with the standard procedure in

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approach flight, which means also less noise. Since this is the case in which the aircraft stays longer in the configuration with lower drag in relation to the standard procedure, it is called the low drag – low pressure procedure. Finally, at 40 – 50 seconds prior to the landing itself, the landing gear is extended, bringing the aircraft to the final landing configuration. From that moment there is enough time for the pilot to balance the flight according to the dive angle path and to finally touch the ground. This procedure brings also certain saving of the consumed fuel which gives it additional significance. Figure 4: Procedure of increasing altitude at which the dive angle signal is detected

Approach in two stages This procedure started to be developed in the USA, but for its implementation the aircraft needs to be fitted with the electronic equipment and additional devices need to be installed at the airport. The same as in the previous procedure, the aircraft flies horizontally at the altitude of 900 metres (3000 ft) up to point B where the pilot receives the special dive angle signal which is set at an angle of 6 degrees and then the aircraft dives at this angle all the way to point C at approximately 300 metres (1000 ft) of altitude, where the pilot detects the signal at the standard Figure 6: Lufthansa procedure dive angle of 3 degrees, at which the final part of approach is performed and finally landing. This approach system has Selective usage of runway another drawback which is of operative nature. In previous The purpose of selective usage of runways (at airports that have practice the pilots landed so that they approached the runway at several runways) lies in the fact that, when possible, those an angle of 3 degrees. In this procedure the pilots have to runways are used that allow the aircraft in the initial takeoff perform the first part of the approach at a double angle. Every phase i.e. in the final approach phase to avoid noise sensitive pilot should attend additional training for such a steep places. It is important that the selective usage of runways approach. should not influence the flight safety so that this method is used if: - the chosen runway is not clean nor dry (if covered by snow, ice, water or rubber scrap); - the meteorological conditions are such that the cloud base is at the altitude lower than 150 metres above the runway selected for landing. Also, if the takeoff and landing conditions are such that the horizontal visibility is less than 1852 m (1NM); - for the selected runway the lateral wind component together with the wind gusts exceeds 29 km/h; - for the selected runway the tail wind component Figure 5: Approach in two stages together with wind gusts exceeds 9 km/h; - “wind shear” is expected or bad weather which may Lufthansa procedure affect the flight in approach or takeoff; The Lufthansa procedure is from the operative point very - the pilot thinks this may endanger the flight safety. interesting since it does not require additional equipment neither onboard aircraft nor on the ground. The approach until Approach / takeoff on curved path detecting the dive angle signal is performed at the altitude of The use of the Microwave Landing System (MLS) makes it 900m (3000 ft) from the standard one, so that the noise possible to use in approach a curved path, and only finish the generated by aircraft will be much lower until reaching the approach by flying at the level of the runway axis. If there is a altitude of about 450 metres. Also, according to this procedure settlement in line with the runway axis, it is possible to avoid the noise will continue to be lower than in the standard flying over it and thus reduce the noise in that place. This procedure since the aircraft drag during flight with less procedure needs special electronic equipment onboard the extended flaps lower, so that this requires lower thrust in aircraft and on the ground. The situation is similar if in takeoff,

ISEP 2006 instead of straight flight the turn is taken so that a settlement is type Fokker 100. Dubrovnik Airlines has in its fleet 2 DC-9 avoided. This method reduces the noise in that place. aircraft. Before the Airbus aircraft Airlines had used Boeing 737 aircraft. The reason for the change to the Airbus 5. INTERNATIONAL REGULATIONS REGARDING fleet is the penalty that has to be paid to other airports due to AIRCRAFT NOISE the noise produced by Boeing aircraft. Every year would pay about 1 million US dollars in order to cover the costs for the noise produced by Boeing aircraft that The restrictions to noisy aircraft started to be implemented on 1 belonged to Chapter 2. The current Airbus fleet of Croatia April 1995. Then, the developed countries stipulated the Airlines belongs to Chapter 3 aircraft. penalty charge for noisy aircraft, and some were banned from operation. Regarding European airlines, they have to comply with the European Union directives, and they are the following: 7. CONCLUSION - phasing out of Chapter 2 aircraft older than 25 years, - replacement of Chapter 2 aircraft less than 25 years With the increase in the number of flights, air traffic is old, becoming a serious problem that needs to be solved at a global - replacement of Chapter 2 aircraft, i.e. their level. The solution for the noise of aircraft will have to find modernization and adaptation to Chapter 3. some alternative ways such as replacement of the current air fleet in Chapter 2 by a new generation of aircraft or some Approaches to solving this problem are different. In the USA, immediate solutions such as fitting of hush-kits and some for instance, the carriers opt for hushing the existing aircraft, special parts into the aircraft, which also results in the reduction whereas the European carriers usually opt for the purchase of of noise. One of the solutions that maybe proposed in the new aircraft, i.e. replacement of the entire fleet. The biggest construction of approach and takeoff runways that are not above problems occur in the states in Latin America, Africa and East the trajectories of residential areas. Considering the future, this . These countries have mainly Chapter 2 aircraft, and is a good solution, but taking into consideration the expansion some have still Chapter 1 aircraft. They cannot allocate the of the urban areas, it is only a matter of time when the necessary means to replace the fleet, and at the same time they residential areas will again find themselves in the trajectory of have to pay also the taxes to the developed countries so that approach and takeoff. While noise is one of the factors within a their aircraft can land at their airports. If a certain airline faces a number of negative factors that are connected to air traffic, problem that their aircraft do not satisfy the basic standards another negative factor should be mentioned, and that is the air related to the future, the airline has three possible options: pollution. Aircraft engines directly pollute the air in the region of ozone and the upper layer of the troposphere. In the areas of - phase out flying with that type of aircraft during the airports there is the highest concentration of pollution, so that it time when this is required by the regulations, and may be said that 45% of pollution can be accounted for by replace them by the new generation aircraft, aircraft, and 45% by road traffic at and around the airport. - perform stipulated and by adequate institutions Other polluters (medical waste, chemicals, etc.) are in a certified engine modifications in order to reduce the majority but they are not to be neglected. The pollution of noise they generate, and thus satisfy the set noise underground waters and water supply areas of big cities and criteria, other residential areas would cause a catastrophe of unthinkable - carry out the replacement of the existing engines that dimensions. The solution to the mentioned problem lies in the do not satisfy the stipulated criteria by new and construction of airports outside the scope of the water supply advanced engines, if the manufacturers have foreseen areas and densely populated areas. Fast development of airports that. and the expansion of urban areas, resulting in big problems

related to noise and air pollution, the human factor will have to 6. CURRENT SITUATION IN CROATIA find a way how to harmonize the development and modernization of air traffic and the "potential adversaries" who On 15 January 1992 the Republic of Croatia became an occur as the consequence of technological development of acknowledged member of the UN and therefore, ratified the airports. Chicago Convention and all the respective legal documents. Within the Republic of Croatia, these regulations refer to the REFERENCES airlines Croatia Airlines, , TradeAir – SunAdria, Dubrovnik Airlines. If we analysed the fleet of every airline, the 1. Aerodromi, Prof.dr.sc. Stanislav Pavlin, Fakultet Croatia Airlines fleet consists of 5 aircraft type Airbus 319, 4 prometnih znanosti, Zagreb aircraft Airbus 320 and 3 aircraft type ATR-42. Air Adriatic 2. Promet i okoliš, Prof.dr.sc. Jasna Golubić, Fakultet contains in its fleet 5 MD-82 and 2 MD-83 aircraft. TradeAir – prometnih znanosti, Zagreb 1999. SunAdria is an airline which operates in cargo and mail 3. Aircraft Noise, M. J.T. Smith, Cambridge University transport but in the mid-2005 it purchased 2 passenger aircraft Press

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4. http://www.aeroport.public.lu/en/environnement/bruit_ avions/index.html 5. http://www.airport-technology.com/ 6. http://www.quietlysuperior.com/History.html 7. http://www.nonoise.org/index.htm